A quantity-time-based dispatching policy for a VMI system

In a Vendor-Managed Inventory (VMI) system, the supplier or the distributor is authorized to coordinate and consolidate the inventories at the retailers. The advantage of VMI is that the bullwhip effect can be minimized and the stock-out situations can also be reduced. Moreover, it provides a framework for synchronizing transportation decisions and hence reduce the transportation cost significantly. In this paper, we present an analytic model for quantity-time-based dispatching policy. The model discussed here takes into the account of the inventory cost, the transportation cost, the dispatching cost and the re-order cost. Since a new inventory cycle begins whenever there is a dispatching of products, the long-run average costs of the model can be obtained by using the renewal theory. We also derive a closed form solution of the optimal dispatching policy.